RU2664139C2 - Pneumatic tyre - Google Patents

Abstract

FIELD: motor vehicle industry.SUBSTANCE: invention relates to automotive industry. On the tread (2) the pneumatic tire (1) is provided with the pair of central main grooves (3) located on the tire equator C both sides, and a pair of shoulder main grooves (4) located on the central main grooves both sides, and on the tire equator both sides is provided with the ground contact middle areas (6), which are restricted with central main grooves (3) and shoulder main grooves (4). Ground contact middle areas (6) are provided with middle inclined grooves (10). Each of the middle inclined grooves (10) extends in the tire equator C direction from the outer end (10o) in the axial direction of tire communicating with the shoulder main groove (4) and the inner end (10i) ends before reaching the central main groove (3). On the middle inclined groove (10) outer end (10o) side, the outer, shallow portion (12) is arranged, having the shallower depth than the middle inclined groove (10) maximum depth.EFFECT: increase in the driving stability.9 cl, 6 dwg, 1 tbl

Description

Technical field

The present invention relates to a pneumatic tire providing good driving stability.

State of the art

JP 2004-210189 describes a pneumatic tire provided with inclined grooves in the middle soil contact area.

However, since the inclined grooves in JP 2004-210189 extend through the entire middle soil contact region, the rigidity of the middle soil contact region is low, and there is the possibility of further improving driving stability.

Description of the invention

The present invention is made to eliminate the above disadvantages, and its main purpose is to provide a pneumatic tire that provides good driving stability.

The present invention relates to a pneumatic tire, in which by providing a pair of central main grooves located on both sides of the tire equator, and a pair of shoulder main grooves located on both sides of the central main grooves; the tread is provided on both sides of the tire equator with middle ground contact areas, which are bounded by central main grooves and shoulder main grooves, characterized in that each middle ground contact area is provided with middle inclined grooves, each of which extends in the tire equator direction from the axial the outer end in communication with the shoulder main groove, and ends so that its axially-inner end does not communicate with the Central main groove; from the side of the outer end, the middle inclined groove is provided with an external shallow-bottomed part having a shallower depth than the maximum depth of the middle inclined groove.

In the pneumatic tire in accordance with the present invention, it is preferable that the middle inclined groove on the side of the above-mentioned inner end is provided with an shallow-bottomed inner part having a shallower depth than the maximum depth of the middle inclined groove.

In a pneumatic tire in accordance with the present invention, it is preferable that the depth of the aforementioned shallow bottom part is lower than the depth of the aforementioned shallow part.

In the pneumatic tire in accordance with the present invention, preferably the bottom surface of the outer shallow bottom part of the groove is provided with a lamella extending along the middle inclined groove.

In a pneumatic tire in accordance with the present invention, the tread is preferably provided on the outside of each shoulder main groove with a shoulder ground contact region, each of which is provided with shoulder lateral grooves including first shoulder lateral grooves and second shoulder lateral grooves whose width is less than the width of the first shoulder lateral grooves, and the first shoulder main grooves and the second shoulder main grooves are alternated in the longitudinal direction of the tire.

In the pneumatic tire in accordance with the present invention, preferably the width of the second shoulder lateral grooves is from 70% to 90% of the width of the first shoulder lateral grooves.

In a pneumatic tire in accordance with the present invention, preferably the shoulder lateral grooves extend to the tread edges, and the angle of the shoulder lateral grooves relative to the tire longitudinal direction is at least 80 degrees at the tread edges.

In a pneumatic tire in accordance with the present invention, a tread is preferably provided between the central main grooves with a central ground contact area, which is a rib provided with central transverse grooves extending from the central main grooves and ending without reaching the tire equator.

In a pneumatic tire in accordance with the present invention, preferably the length of the central lateral grooves in the axial direction of the tire is not more than 30% of the width of the central area of contact with the ground.

In the present invention, middle inclined grooves are provided in each middle soil contact area. Each middle inclined groove contains an outer end in the axial direction of the tire in communication with the shoulder main groove, and an inner end in the axial direction of the tire, not in communication with the central main groove.

Thus, the middle inclined grooves allow a water film to be drawn between the middle contact areas with the ground and the road surface to the outside of the tire through the shoulder main grooves.

Moreover, since the middle inclined grooves do not extend through the entire middle soil contact area, the middle soil contact areas are highly stiff and can provide good driving stability.

In addition, since the outer end of the middle inclined groove is provided with an external shallow-bottomed portion having a shallower depth than the maximum depth of the middle inclined grooves, it is possible to effectively suppress the deformation of the middle ground contact areas when cornering, and driving stability can be further improved.

Brief Description of the Drawings

In FIG. 1 is an exploded view of a tread of a pneumatic tire according to an embodiment of the present invention.

In FIG. 2 is a partial enlarged view of the middle ground contact area shown in FIG. one.

In FIG. 3 is a cross-sectional view AA shown in FIG. 2.

In FIG. 4 is a partially enlarged perspective view of the inner side in the axial direction of the tire of the middle contact area with the ground.

In FIG. 5 is a cross-sectional view BB shown in FIG. one.

In FIG. 6 shows an incomplete enlarged perspective view of the shoulder area of contact with the ground.

Hereinafter, an embodiment of the present invention is described with reference to the drawings. In FIG. 1 is an exploded view of a tread 2 of a pneumatic tire 1 according to an embodiment of the present invention. The pneumatic tire in the present embodiment is presented as a radial tire 1 for cars, in which the rotation direction R is set. The direction of rotation R is shown on the sides of the pneumatic tire 1 using signs, symbols or the like.

The tread 2 is provided with a pair of central main grooves 3, 3 located on both sides of the tire equator C, and a pair of shoulder main grooves 4, 4 located on both sides of the central main grooves. Preferably, these main grooves 3 and 4 have a depth of, for example, at least 6 mm, more preferably from 7 to 11 mm, so that satisfactory drainage properties can be obtained.

The central main groove 3 extends, for example, in a straight line along the longitudinal direction of the tire. In this way, a good drainage effect can be obtained in the central region of the tread 2. The central main groove 3 can also be made in a zigzag shape.

The central main groove 3 has a relatively large width. In order to obtain favorable drainage properties, preferably the central main groove 3 has a width of, for example, at least 3%, more preferably at least 5% of the tread width TW. On the other hand, in order to obtain good driving stability, the width of the central main groove 3 is preferably, for example, not more than 10%, more preferably not more than 8% of the tread width TW.

In this document, the tread width TW is the axial distance between the edges Te of the tire tread in a normal state. A “normal state” is a state of tire 1 in which it is mounted on a standard rim, inflated to normal pressure and not loaded with any load. Unless otherwise indicated, various tire sizes are values measured in a given normal condition.

A “standard rim” is a wheel rim established for a tire by a standard included in the standardization system on which the tire is based, for example, a “standard rim” in the JATMA system (Japan Association of Automobile Tire Manufacturers), a “design rim” in the TRA system (Association rims and tires) and “measuring rim” in the ETRTO system (European Technical Organization for Rims and Tires).

"Normal internal pressure" is the air pressure set for the tire by the standard included in the standardization system on which the tire is based, for example, "maximum air pressure" in the JATMA system, the maximum pressure value given in the table "Tire load limits at various pressures cold pump ”in the TRA system and“ pump pressure ”in the ETRTO system. However, in the case of passenger car tires, the “normal internal pressure” is uniformly 180 kPa.

"Tread edges" are the axially external positions of the tread contact with the ground when the tire is in normal condition, loaded with normal load and pressed against a flat surface at a camber angle of zero degrees.

“Normal load” is the normal load set for the tire by the standard included in the standardization system on which the tire is based, for example, the normal load is the “maximum load capacity” in the JATMA system, the maximum value given in the above table in the TRA system and “ lifting capacity ”at ETRTO. However, in the case of tires for passenger cars, the normal load is a load of 88% of the above load.

For example, the shoulder main grooves 4 extend straight along the longitudinal direction of the tire. Thus, a good drainage effect can be obtained on the outer area of the tread 2. The shoulder main groove 4 can also be made in a zigzag shape.

In order to obtain favorable drainage properties, preferably the shoulder main grooves 4 have a width of, for example, at least 2%, more preferably at least 3% of the tread width TW. In order to obtain good driving stability, preferably the width of the shoulder main grooves 4 is, for example, not more than 9%, more preferably not more than 7% of the tread width TW. In this embodiment, the shoulder main groove 4 has a smaller width than the width of the central main groove 3.

By providing the central main grooves 3 and the shoulder main grooves 4, the tread 2 is divided into five areas of contact with the ground. Five areas of contact with the ground include:

the central area 5 of contact with the soil, limited by the Central main grooves 3.3

a pair of middle ground contact areas 6 delimited by the central main grooves 3 and the shoulder main grooves 4, and

a pair of shoulder areas 7 of contact with the soil, defined outside the shoulder main grooves 4.

The middle ground contact areas 6 on both sides of the tire equator C have a great influence on driving stability when cornering. In the present invention, in order to provide good driving stability and drainage properties, each of the middle soil contact areas 6 is provided with middle inclined grooves 10.

In FIG. 2 is a partial enlarged view of the middle ground contact area 6 shown in FIG. 1. Each of the middle inclined grooves 10 extends from the outer end 10 ° to the inner end 10i in the axial direction of the tire.

The outer end 10o of the middle inclined groove 10 is in communication with the shoulder main groove 4. The inner end 10i of the middle inclined groove 10 is located in front of the central main groove 3 without communication with it. Accordingly, the middle ground contact region 6 is formed in the form of a rib, which is a ground contact region extending continuously in the tire longitudinal direction. Such ribs have a higher longitudinal stiffness compared to a number of blocks and serve to improve driving stability.

Each of the middle inclined grooves 10 extends toward a later contact with the ground in the direction of rotation R of the tire from the inner end 10i to the outer end 10o. As a result, since the middle inclined groove 10 comes into contact with the soil starting from the inner end 10i, water in the middle inclined groove 10 is pushed towards the outer end 10o under the influence of contact pressure on the tire ground during movement, and water is effectively discharged from the main shoulder grooves 4.

In order to provide well-balanced driving and drainage stability characteristics, it is preferable that the distance D in the axial direction of the tire between the inner end 10i of the middle inclined groove 10 and the central main groove 3 is approximately 30% to 40% of the width Wm in the axial direction of the tire of the middle ground contact region 6 .

The middle inclined groove 10 includes an outer portion 10a extending axially inward from the outer end 10o and an inner portion 10b extending axially outward from the inner end 10L For example, the outer portion 10a is at a greater angle with respect to the longitudinal direction of the tire than the inner portion 10b. Thus, the middle inclined groove 10 is made in the form of a curved groove, which is curved smoothly.

The middle inclined grooves 10, as described above, can increase lateral stiffness on the axially external side of the middle soil contact region 6, while improving drainage properties on the axially internal side of the middle soil contact region 6. In a preferred embodiment, the angle a1 of the inner part 10b relative to the longitudinal direction of the tire is from 35 to 60 degrees, and the angle a2 of the outer part 10a relative to the longitudinal direction of the tire is from 5 to 25 degrees.

In FIG. 3 is a cross-sectional view AA of the middle inclined groove 10 shown in FIG. 2. As can be seen from FIG. 3, the middle inclined groove 10 is provided with an outer shallow bottom part 12 from the outer end 10o. The outside shallow bottom part 12 has a depth (do) that is less than the maximum depth (dm) of the middle inclined groove 10. On the outside of the middle ground contact area 6 such an external shallow-bottomed portion 12 weakens the influence of the middle inclined groove 10, which is manifested in a decrease in the rigidity of the area of contact with the ground. Thus, the outer shallow bottom portion 12 suppresses deformation of the middle ground contact region 6 when cornering and improves driving stability.

In order to improve the above effects, it is more preferable that the depth (do) of the outer shallow bottom portion 12 be less. On the other hand, if the depth (do) of the outer shallow bottom portion 12 becomes smaller, drainage properties and noise characteristics may deteriorate. From this point of view, the minimum depth (do) of the outer shallow bottom portion 12 is not less than 45%, more preferably not less than 50% and preferably not more than 65%, more preferably not more than 60% of the maximum depth (dm) of the middle inclined groove 10.

In a preferred embodiment, the outer shallow bottom portion 12 includes a base portion 12a extending in the longitudinal direction of the groove with a minimum depth (do), and an inclined portion 12b extending in the longitudinal direction of the groove from the main portion 12a so that the depth of the groove gradually increases. The inclined portion 12b smoothly extends to the deepest point 15, which has a maximum depth (dm). Such an inclined portion 12b can suppress a sharp change in stiffness between the main portion 12a of the outer shallow bottom portion 12 and the deepest point 15 and effectively prevent stress concentration.

In this embodiment, the outer shallow bottom portion 12 extends a predetermined distance, including the outer end 10 ° of the middle inclined groove 10. For the above effect to manifest sufficiently, preferably the outer shallow bottom portion 12 extends for example 4 to 8 mm along the middle inclined groove 10.

As shown in FIG. 2 and 3, the bottom surface of the outer shallow bottom portion 12 is provided with a lamella 13 extending along the middle inclined groove 10. For example, the lamella 13 is an incision whose width is 1 mm or less. Even if the tread 2 is worn so that the outer shallow bottom portion 12 comes into contact with the ground, the lamella 13 can connect the middle inclined groove 10 with the shoulder main groove 4 and prevent deterioration of the drainage properties. Moreover, during movement, air compressed in the middle inclined groove 10 is discharged into the shoulder main groove 4 through the lamella 13. Thus, the lamella 13 suppresses an increase in pumping noise generated in the middle inclined groove 10 and the like.

Preferably, the lamella 13 extends in a central position across the width of the outer shallow bottom portion 12. The depth of the lamella 13 is not particularly limited, but preferably, for example, as shown in FIG. 3, the lower portion 13a of the lamella 13 reaches a position at a maximum depth (dm) of the middle inclined groove 10. Such a lamella 13 allows for the above effect, which is manifested before the final wear.

In a preferred embodiment, the middle inclined groove 10 is provided on the side of the inner end 10i with an inner shallow bottom portion 14. The inner shallow bottom part 14 has a shallower depth than the maximum depth (dm) of the middle inclined groove 10. The inner shallow bottom part 14 is able to further weaken the influence of the middle inclined groove 10. manifested in a decrease in rigidity of the middle area 6 of contact with the soil, while providing drainage in the middle inclined groove.

In rectilinear motion, a higher contact pressure on the ground usually acts on the axially inner side of the middle ground contact region 6 compared to the outside. Thus, based on such a difference in ground pressure, it is preferable, for example, that the inner shallow bottom portion 14 has a shallower depth than the outer shallow bottom portion 12 or that it extends a greater distance along the longitudinal direction of the groove than the outer shallow bottom portion 12. In the present embodiment the depth (di) of the inner shallow bottom portion 14 is less than the depth (do) of the groove of the outer shallow bottom part 12, and it extends along the longitudinal direction of the groove to a greater distance than the outer shallow bottom part 12. By especheniya melkodonnoy inner part 14 can further improve the stability of the tire during straight running.

In order to further enhance the above effect, it is more preferable that the depth (di) of the groove in the inner shallow bottom portion 14 is less. On the other hand, if the depth (di) of the groove in the inner shallow bottom part 14 is too small, drainage from the middle inclined groove 10 may deteriorate. From this point of view, the minimum depth (di) of the inner shallow bottom part 14 is at least 10%, more preferably not less than 15% and preferably not more than 35%, more preferably not more than 30% of the maximum depth (dm) of the middle inclined groove 10.

In a preferred embodiment, the inner shallow bottom portion 14 includes a base portion 14a extending in the longitudinal direction of the groove with a minimum depth (di) and an inclined portion 14b extending in the longitudinal direction of the groove from the main portion 14a so that the depth of the groove gradually increases. The inclined part 14b smoothly extends to the deepest part 15. Such an inclined part 14b allows you to suppress a sharp change in stiffness between the main part 14a of the inner shallow bottom part 14 and the deepest part 15 and allows you to effectively prevent stress concentration.

In this embodiment, the inner shallow bottom portion 14 extends a predetermined distance, including the inner end 10i of the middle inclined groove 10. In a preferred embodiment, the inner shallow bottom portion 14 extends over a distance of 40% to 60% of the length of the inner portion 10b of the middle inclined groove 10.

The deepest part 15 of the middle inclined groove 10 is provided between the outer shallow bottom part 12 and the shallow bottom part 14. Preferably, for example, the deepest part 15 has a maximum depth (dm) of about 65-100%, more preferably 70-90% of the depths of the central main groove 3.

The deepest part 15 of the middle inclined groove 10 is provided, for example, between the outer part 10a and the inner part 10b of the middle inclined groove 10 (i.e., it includes a curved part). In a preferred embodiment, the inclined portion 14b of the inner shallow bottom portion 14 has a smoother inclination than the inclined portion 12b of the outer shallow bottom portion 12. Thus, it is possible to further reduce the stiffness change on the axially inner side of the middle ground contact region 6, where the ground contact pressure is high .

As shown in FIG. 1 and 2, in the present embodiment, the middle ground contact region 6 also comprises slots 19. The slots 19 are located in the tire longitudinal direction with substantially the same step as the middle inclined grooves 10. The slots 19 extend from the central main groove 3 in the axial direction tire directions and end within the middle area 6 of contact with the ground. In a preferred embodiment, the slots 19 extend substantially at the same angle as the outer part 14a of the middle inclined groove 10. Such slots 19 maintain a well-balanced stiffness on the axially inner side and the outer side of the middle ground contact region 6 and prevent uneven wear.

In FIG. 4 is a partially enlarged perspective view of the inner side in the axial direction of the tire of the middle ground contact region 6. Preferably, for example, the depth dc of the slot 19 is in the same range as the maximum depth (dm) of the middle inclined groove 10. In a preferred embodiment, the corner portion X1 from the obtuse side where the slot 19 and the central main groove 3 intersect are provided with a first recess twenty.

The first recess 20 is a bevel provided in the corner portion formed by the tread surface 6a of the middle ground contact area 6, the wall beyond the walls of the central main groove 3 and the wall surface 19a of the slot 19. As shown in FIG. 2, the first recess 20 gradually decreases in width in the axial direction of the tire with increasing distance from the slot 19, forming a triangular shape in a plan view. The first recess 20 allows you to reduce the concentration of stresses in the vicinity of the slot 19 and to prevent delamination of the rubber and the occurrence of cracks in it.

Returning to FIG. 4, in another preferred embodiment, the corner portion X2 on the side of the acute angle where the slot 19 and the central main groove 3 intersect is provided with a second recess 21. The second recess 21 is a bevel that is inclined inward in the radial direction of the tire to the top of the corner portion X2 relative to the tread surface 6a of the middle ground contact area 6. The second recess 21 is also made with the formation of a triangular shape in a plan view. This second recess 21 also allows you to weaken the stress concentration near the slot 19 and prevents the delamination of the rubber and the occurrence of cracks in it.

As shown in FIG. 1 and 2, the central soil contact area 5 is located between the middle soil contact areas 6, 6. The design of the central soil contact area 5 is not particularly limited. In a preferred embodiment, the central soil contact area 5 is provided with central transverse grooves 23.

On each side of the central ground contact region 5, the central lateral grooves 23 are located in the longitudinal direction of the tire with substantially the same pitch as the middle inclined grooves 10. The central lateral grooves 23 extend in the direction of the tire equator C from the respective central main grooves 3 and end within the central area 5 of contact with the soil, not reaching the equator C of the tire. Thus, the central area 5 of contact with the soil is made in the form of a rib extending continuously in the longitudinal direction of the tire. The central lateral grooves 23 reduce the stiffness of the central soil contact area 5 in the longitudinal direction of the tire so as to bring it closer to the stiffness of the middle soil contact area 6 in the tire longitudinal direction. Thus, the rigidity of the tread 2 varies moderately from the tire equator C to the middle ground contact region 6, and driving stability is further improved.

As shown in FIG. 2, the axial length L of the tire of the central transverse grooves 23 is preferably not more than 30% of the width Wc of the central soil contact region 5. If the length L is more than 30% of the width Wc of the central soil contact region 5, driving stability may be impaired. In addition, the depth of the central transverse groove 23, for example, is preferably set in the same range as the range for the maximum depth (dm) of the middle inclined groove 10.

In a preferred embodiment, the angular part XZ from the side of the acute angle where the central transverse groove 23 and the central main groove intersect are provided with a third recess 24. The third recess 24 is a bevel that is inclined radially inward from the tire to the top of the angular part XZ from the tread surface of the central region 5 contacts with soil. The third recess 24 is formed to form a triangular shape in a plan view. Such a third recess 21 allows you to reduce the stress concentration near the Central transverse groove 23 and to reduce the delamination of the rubber and the occurrence of cracks in it.

Outside in the axial direction of the tire of the middle ground contact regions 6 are the shoulder ground contact regions 7. For example, each of the shoulder regions 7 in contact with the ground is provided with shoulder lateral grooves 25. The shoulder lateral grooves 25 extend from the shoulder main grooves 4 to the edges Te of the tread. Accordingly, the shoulder contact regions 7 are divided into shoulder blocks 28. In order to provide improved driving stability by increasing the lateral stiffness of the shoulder blocks 28, the shoulder lateral grooves 25 extend substantially in the axial direction of the tire. In yet another preferred embodiment, at positions at the tread edges Te, the angles a3 relative to the longitudinal direction of the tire of the shoulder lateral grooves 25 are preferably 80 to 90 degrees.

In the present embodiment, the shoulder lateral grooves 25 include a first shoulder lateral grooves 26 having a width G1 and second shoulder lateral grooves 27 having a width G2 that is smaller than the width of the first shoulder lateral grooves 26. Preferably, the first shoulder lateral grooves 26 and the second shoulder lateral grooves grooves 27 are arranged alternating in the longitudinal direction of the tire. This arrangement of the shoulder lateral grooves 25 allows you to disperse the noise from the step of the tire tread pattern created by the shoulder lateral grooves 25 when moving over a wide range of frequencies and provide good noise characteristics. On the other hand, in order to ensure good noise characteristics, while preventing uneven wear of each of the shoulder blocks 28, preferably, the width G2 of the second shoulder lateral grooves 27 is from 70% to 90% of the width G1 of the first shoulder lateral grooves 26.

In a preferred embodiment, on each side of the tire equator C, the total number of shoulder lateral grooves 25 is two times the total number of middle inclined grooves 10. In other words, in the middle ground contact region 6, the middle inclined grooves 10 are located with a relatively low density, and therefore stiffness the middle soil contact area 6 is further increased.

In yet another preferred embodiment, the inner ends of the first shoulder lateral grooves 26 having a large width are positioned so that they smoothly transition into the middle inclined grooves 10 through the shoulder main groove 4. Thereby, water pushed from the middle inclined grooves 10 axially outward when moving , it is possible to effectively retract the tread 2 outward from the shoulder main grooves 4 and the first shoulder lateral grooves 26 having a large width.

In FIG. 5 is a cross-sectional view BB shown in FIG. 1. The shoulder lateral grooves 25 include a main body 25a having a maximum depth (ds) and an shallow-bottomed inner part 25b having a shallower depth (dt) than the maximum depth (ds). The inner shallow bottom portion 25b is located on the axial direction of the shoulder lateral groove tire 25 from the inner end. The inner shallow bottom portion 25b can suppress deformation in the longitudinal direction of the tire of each of the shoulder blocks 28 during movement and braking, while maintaining drainage properties and effectively suppressing, for example, sawtooth wear.

To further enhance the above effects, preferably the depth (dt) of the inner shallow bottom portion 25b of the shoulder lateral groove 25 is from about 30% to 70% of the depth of the shoulder main groove 4. For the same purpose, the length L4 of the inner shallow bottom portion 25b of the shoulder lateral groove 25 is preferably from about 10% to 20% of the length L3 in the axial direction of the tire of the shoulder main groove 4.

In FIG. 6 is a partial enlarged perspective view of the shoulder region 7 of the ground contact. To further improve driving stability, the shoulder block 28 may be provided with a fourth recess 29.

The fourth recess 29 is located in the corner portion X4 formed by the shoulder main groove 4 and the shoulder lateral groove 25, which is located on the initial contact side in the rotation direction R of the tire of the shoulder unit 28. The fourth recess 29 is a bevel inclined inward in the radial direction of the tire to the corner part X4 from the tread surface of the shoulder block 28. The fourth recess 29 is made with the formation of a triangular shape in a plan view (Fig. 2). Such a fourth recess 29 suppresses deformation of the shoulder block 28 near the corner portion X4. Therefore, the contact of the block with the soil is improved and driving stability is improved. In addition, the fourth recess 29 can reduce the delamination of the rubber and the occurrence of cracks in it.

To further improve driving stability, the shoulder block 28 may be provided with a fifth recess 30. The fifth recess 30 is located in the corner portion X5 formed by the shoulder main groove 4 and the shoulder lateral groove 25, which is located on the later contact side in the rotation direction R of the shoulder block tire 28. The fifth recess 30 is a bevel inclined inward in the radial direction of the tire from the tread surface 28a of the shoulder block 28 in the direction of the corner portion X5. The fifth recess 30 is provided on the side of the later contact in the rotation direction R of the tire of the fourth recess 29 and is formed with a triangular shape in a plan view (Fig. 2), while such a triangle is longer in the longitudinal direction of the tire and is inverted compared to the fourth recess 29. Such a fifth recess 30 suppresses deformation of the shoulder block 28, even when a large lateral force is applied to it when cornering. Therefore, the contact of the shoulder block 28 with the soil is improved, and driving stability is improved.

The tread 2 of the present embodiment uses a pattern in which half of the tread on one side of the tire equator C and half of the tread on the other side of the tire equator C are substantially linearly symmetrical with respect to the tire equator C but offset in the tire longitudinal direction. With this pattern, since the middle inclined grooves 10 and the shoulder lateral grooves 25 on both sides of the tire equator C come into contact with the ground when the positions are mutually offset, improved noise characteristics can be obtained.

Although a detailed description of embodiments of the present invention is provided, the present invention can be implemented in various forms and is not limited to the embodiments presented.

Examples

To confirm the effects of the present invention, experimental radial tires for passenger cars of size 205 / 55R16 were made based on the technical characteristics presented in Table 1, and their various characteristics were tested. Test methods are described below.

Driving Stability Test A professional test driver drove a passenger car with test tires installed under the conditions listed below, and the driver felt the stability of the tire was evaluated along the test route. Results were expressed in points, and a higher value meant a better result. Rim Size: 6.6J Internal Pressure: 200 kPa

Noise test

We measured the external noise of the car (OA value) when the car was moving along the asphalt road surface at a speed of 60 km / h. The smaller the value, the better.

Wear test

Using a wear test machine, sawtooth wear was measured. The results are presented as an indicator of the degree of wear, the lower the value of the indicator, the better the result.

The test results are presented in table 1.

The test results confirm that the tires of the examples of the invention provide significantly improved driving stability compared to tires of the comparative examples.

Designation List

1 - pneumatic tire

2 - protector

3 - central main groove

4 - shoulder main groove

5 - the central area of contact with the ground

6 - middle area of contact with the ground

7 - shoulder area of contact with the ground

10 - middle inclined groove

12 - external shallow bottom part

13 - lamella

14 - inner shallow bottom part

15 - the deepest part

23 - Central transverse groove

25 - shoulder transverse groove

26 - the first shoulder lateral grooves

27 - second shoulder lateral grooves

dm - maximum groove depth

Claims (9)

1. A pneumatic tire in which by providing a pair of central main grooves located on both sides of the tire equator, and a pair of shoulder main grooves located on both sides of the central main grooves, the tread is provided on both sides of the tire equator with middle ground contact areas , which are limited by the central main grooves and shoulder main grooves, characterized in that each middle area of contact with the ground is equipped with middle inclined grooves, each of which passes in the direction of the tire equator from the axially outer end communicating with the shoulder main groove, and ends so that its axial inner end does not communicate with the central main groove, and from the side of the outer end, the middle inclined groove is provided with an outer shallow bottom portion having a shallower depth, than the maximum depth of the middle inclined groove. 2. The pneumatic tire according to claim 1, in which the middle inclined groove from the side of the inner end is provided with an shallow-bottomed inner part having a shallower depth than the maximum depth of the middle inclined groove. 3. The pneumatic tire according to claim 2, in which the depth of the above-mentioned inner shallow bottom portion is less than the depth of the above-mentioned shallow-bottom outer part. 4. The pneumatic tire according to claim 1, in which the bottom surface of the outer shallow bottom part of the groove is provided with a lamella running along the middle inclined groove. 5. The pneumatic tire according to claim 1, wherein the tread is provided on the outside of each shoulder main groove with a shoulder ground contact region, each of which is provided with shoulder lateral grooves including first shoulder lateral grooves and second shoulder lateral grooves whose width is less than the width of the first shoulder lateral grooves, and the first shoulder main grooves and the second shoulder main grooves are alternated in the longitudinal direction of the tire. 6. The pneumatic tire according to claim 5, in which the width of the second shoulder lateral grooves is from 70 to 90% of the width of the first shoulder lateral grooves. 7. The pneumatic tire according to claim 5 or 6, wherein the shoulder lateral grooves extend to the edges of the tread and the angle of the shoulder lateral grooves relative to the longitudinal direction of the tire is at least 80 degrees at the edges of the tread. 8. The pneumatic tire according to claim 1, wherein the tread is provided between the central main grooves with a central ground contact area, which is a rib provided with central transverse grooves extending from the central main grooves and ending without reaching the tire equator. 9. The pneumatic tire according to claim 8, in which the axial length of the central longitudinal grooves is not more than 30% of the width of the central area of contact with the ground.

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